The 91,000-acre swath of swamp and prairie that Edward Vose "E.V." Babcock bought in 1919 is today the only unbroken avenue of undeveloped land between Lake Okeechobee in the east and Charlotte Harbor on the Gulf Coast.

Babcock, a lumber magnate, bought the 143-square-mile parcel for its longleaf pine trees. Today, his heirs operate a cattle ranch there along with logging, mining and sod-farming operations. The relative lack of development has made the ranch an ecological treasure to many, however. Just north of the Caloosahatchee River, the property is home to more than 20 protected animal species, including the Florida panther and the Sandhill crane; some family members offer "swamp buggy" eco-tours of the property.

The heirs' decision in 2001 to put the ranch up for sale has touched off a fierce battle. Agencies like the South Florida Water Management District and environmental groups consider the ranch essential to the health of the western Everglades, including the Caloosahatchee. But with Census projections showing an impending population explosion in Charlotte County, others believe the sprawling tract, which is as large as Cape Coral, is a natural spot for residential development. One proposal suggested setting aside 44,000 acres for preservation and opening up 19,000 acres to development.

Charlotte County Commissioner Adam Cummings considers plans for residential developments on Babcock Ranch a "growth management nightmare" that he will fight "tooth and nail." Also, Cummings says, Babcock's wetlands are a significant water source that should not be compromised.

But it's unclear whether conservationists can put together a deal that will satisfy family members, who declined comment for this article. The land is worth between $450 million and $460 million, according to two state appraisals. In April, because of a legal technicality involving the structure of the proposed sale, the family rejected a $455-million offer from the state using $199,000 in Florida Forever funds. The terms would have opened up 12,000 acres for development.

The Southwest Florida Regional Planning Council, Lee and Charlotte counties and local and regional organizations have created a non-profit foundation, the Babcock Preservation Partnership, to try to purchase the land. So far the group has raised $180,000 and $150,000 in pledges.

After the deal with the state fell apart in April, ranch owners decided to take a breather from negotiations. Conservationists are using the time to step up their fund-raising efforts and look at more creative financing methods.

The stakes are huge, says Matt Bixler, policy director for the Conservancy of Florida. "There's a concern that every square inch of Florida could be developed," he says. "It really points to the reason why we need to protect an area like Babcock Ranch."